Many of light-emitting elements that are used for displays have a structure in which a layer including a luminescent material is sandwiched between a pair of electrodes, and luminescence is produced when an exciton formed by recombining an electron injected from one of the electrodes and a hole injected from the other electrode returns to the ground state.
Regarding these light-emitting elements, studies for improving a luminous efficiency and stability and preventing increase in driving voltage have been conducted.
For example, Patent Document 1 discloses a highly durable organic thin-film light-emitting element that is able to keep light-emitting performance. According to Patent Document 1, it is disclosed that a lower driving voltage for the light-emitting element is achieved by using a metal oxide that has a higher work function, such as a molybdenum oxide, for an anode.
In addition, crystallization of a material constituting a light-emitting element is cited as a cause of deterioration of the light-emitting element. Therefore, a material that is not likely to be crystallized is desired, and for example, Patent Document 2 disclosed a heat-resistant organic material that has a higher glass-transition temperature.
[Patent Reference 1]
Japanese Patent Application Laid-Open No. 9-63771
[Non-Patent Reference 1]
WO Publication No. WO00/27946